A. Field of Invention
This invention generally relates to motor drive systems for automated closure components such as vehicle windows. In particular, the invention relates to motor drives that can recover position information of the closure component in the event of a power failure.
B. Description of the Related Art
Powered controllers for closure components such as sunroofs and window lift systems offer automatic closure with an anti-pinch safety feature as a convenience to the customer. These controllers need to maintain accurate position information of their closure components in order to allow safe and effective anti-pinch capability. These systems include a motor drive system operated by an Electronic Control Unit (ECU).
During operation, the ECU typically does not save position information until the motor stops at the end of a closure operation. However, in the event of a power supply interruption, the ECU loses power without saving position information. The system must then disable the automatic closure operation until the motor can reacquire the position of the closure component.
In order to prevent the disabling of the automatic operation, a large capacitor is typically used to provide a short supply of emergency power to the ECU during interruptions of primary power. This large capacitor keeps the ECU operational long enough for the motor to come to a stop, at which time the ECU can save the position information and prevent loss of anti-pinch. However, such capacitors are large and expensive components and add considerably to the overhead of the system.